In downlink transmission of a Long Term Evolution (LTE) Rel-8/9/10 communications system, a base station such as an evolved Node Base (eNB) sends a physical downlink shared channel (PDSCH) and a corresponding physical downlink control channel (PDCCH) to each scheduled user equipment according to a scheduling result.
The PDSCH carries data sent by the eNB to the scheduled user equipment, and the PDCCH carries scheduling information of the corresponding PDSCH. The scheduling information includes physical channel resources allocated to the UE, information about a modulation and coding scheme (MCS) that is specifically used, and the like. In a subframe, the PDCCHs of all scheduled user equipments are multiplexed together, and are then sent in a PDCCH region, and the PDSCH is sent in a PDSCH region. Each PDCCH is formed by 1/2/4/8 control channel elements (CCE). In a further evolution of the LTE Rel-10 system, MU-MIMO (Multiple User Multiple Input Multiple Output) and coordination between multiple cells need to be supported to improve system performance. These technologies lead to an increase in a quantity of simultaneously scheduled user equipments. However, the PDCCH has a limited capacity, which restricts a quantity of user equipments that can be scheduled by one subframe. Therefore, the PDCCH is enhanced in the prior art, that is, some resources are separated from the original PDSCH region to transmit an enhanced PDCCH, that is, enhanced-physical downlink control channel (E-PDCCH). Meanwhile, the UE can demodulate the E-PDCCH based on a demodulation reference signal (DMRS), which increases the capacity of the PDCCH and the quantity of simultaneously scheduled user equipments. Each E-PDCCH is formed by 1/2/4/8 logical elements similar to CCEs, where the logical elements are referred to as enhanced-control channel elements (E-CCEs).
In the prior art, after the E-PDCCH is sent, the user equipment uses the DMRS to perform channel estimation, and demodulates the E-PDCCH. In this case, the base station needs to use the PDCCH to dynamically notify the user equipment of a DMRS antenna port number that needs to be used. However, if the subframe that carries the E-PDCCH has no PDCCH, the user equipment is unable to obtain the DMRS antenna port number that is used to demodulate and receive the E-PDCCH.